Telephone-exchange system.



No. 646,682. v Patented Apr. 3, I900.- E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

(Applicationfiled Apr. 21, 1899.)

(No Model.)

. UNITED STATES PATENT O FICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO THE SUN ELECTRIC MANUFACTURING COMPANY, OF NE\V JERSEY.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part Of Letters Patent N0. 646,682, dated April 3, 1900.

Application filed April 21, 1899. Serial No. 713,883. (No model.)

To all whom ii; may concern: same wires or conductors as the talking-cir- Be it known that I, EDWARD E. CLEMENT, a cuits utilize the latter in such a relation that citizen of the United States, residingin \Vashthe efiect of signaling-current upon the balington, in the District of Columbia, have inance or the general efficiency of the talking- 5 vented acertain new and useful Improvement circuits is practically nil. Stated more spein Telephone-Exchange Systems, of which the cifically, the signaling circuits are really following is a specification, reference being phantom circuits formed of portions of the had to the accompanying drawing, forming a talking-circuits in multiple relation.- part thereof, in which the same letters and In my former case, referred to above, sevto figures of reference point out the same parts eral generators were required. In the presthroughout. ent case but two are utilized, one being a My invention relates to telephone-exchange common source of current for all incoming systems of the type described in my prior apand supervisory signals and the other furplication, Serial No. 683,652, filed June 16, nishingalternatingcurrent for outgoingcalls. 15 1898. I have chosen to call such systems Referring to the accompanying drawing, semiautomatic, because in making a conthe figure is a diagram of a system embodynection between two subscribers one of the .ing my invention, the apparatus throughout two selections usually required to be perbeing shown in a simple conventional form. formed by the operators is performed by mech- X and Y are two subscribers stations, each 2o anism placed under the control of the calling connected with a central oifice by line-wires subscriber in making connection with his I and 2. As the apparatus at the two stalinethat is to say, instead of an answerin g tions isidentical in every particular, the parts operator having to ask the number of the line beinglettered the same throughout, a descripwanted and from that number deduce the tion of the station Xwill suffice for both. At 2 5 number of the board-section upon which the this station T is the usual transmitter; R, the wanted-line terminal is located (the invention receiver; I, the induction-coil; Q, the ringer, applying particularly to divided central or and S S the switch. The switchconsists of trunking systems) one of the two selections, two movable members connected together mepreferably that of the board-section, is perchanically, but insulated from each other, 3o formedbymechanism controlled from thesub-' each connected to one of the line-wires and scribers station, leaving the operator upon normally, when the receiver is upon the hook, that section to ask the number wanted and serving to connect the line-wires with the cirto complete the connection. cuit of the ringer Q and disconnect them from The main object of the present invention the talking set. This condition is shown at 35 is to separate the signaling from the talking station Y. Theinduction-coilIhas two windcircuits. It has been found somewhat undeingsi't, the latter of which-the sec0ndaryis sirable to talk through contacts which might in' series with the receiver-windings and conbe somewhat uncertain in their action; but nected with the upper contacts of the switchby care in manufacture and the use of platihook, so as to be connected to the line-wire o 40 nu in points wherever possible the objections when the hook rises. The other winding i is to this are reduced to a minimum. It has in a local circuit with the transmitter T and been found more undesirable, however, to' a battery i, this circuit also being closed by signal over the same circuits for various reathe switch-hook whenit rises. Fromthe midsons. Moreover, it is possible by substitutdle point of the secondary-winding?aground- 5 45 inganormally-closed for-a normally-open sigtap Z 8 9 is led. Included in this ground-tap nalingcircuit to use the same circuits and a is avariable signal mechanism W'. This conportion of the same mechanism which persists, essentially, of a toothed wheel adapted forms the selection in the first place for purto be set to send any desired number of imposes of supervision and clearing out. pulses, a detent-lever w for retaining the I00 50 In designing the present system the signalwheel in its set position, a magnet to, controling-circuits while they embody in part the ling the detent-lever, a stop w determining the zero-point of the wheel, and a pen 7, normally resting upon a solid portion or tooth of the wheel, but adapted to pass into its notches as it revolves, thus breaking the circuit a predetermined numberot times. This signaling mechanism is only shown in a diagrammatic way, as it is supposed to be of any desired pattern, various mechanisms for the purpose being well known in the art. Anyclosed-circuit signal movement having a properlywound detent-magnet will answer.

I have shown the receiver R connected to one side of the secondary winding of the induction-coil. YVhile this is the usual arrangement, it is only adopted here for illustration, as in practice it is necessary that the receiver should occupy a balanced position with regard to the line-wires, and this can only be secured by either interposing it between the two halves of the secondary winding and tapping the middle point of its winding or bridging it across the secondary terminals.

At the central otiice the line-wires are connected to springs of line-jacks J, which normally rest upon contact-anvils j, from which conductors 3 are led to line-annunciators A, having signals a, and thence by wires 4 to the bus-bar 5 of a direct-current generator G, which is grounded through the wire 6. The magnets of the annunciators A are of higher resistance than magnets 10, and the voltage of the generator G is such that when a complete ground-circuit is closed with these mag nets in series the line-magnet A, having a greater number of turns, will be energized sufficiently to display its signal, whereas the magnet 10 will be powerless to release the signal-wheel as long as the series relation continues.

The line-annunciators and line-jacks of stations X and Y are supposed to be located upon ditferent board-sections, although, as

will appear later, the operation would be precisely the same if they were upon the same section and were to be connected. The annunciator A and its jack J are supposed to be located at the desk of the chief or trouble operator. The aununciator A is connected, as will be seen, in a very similar manner to that in which the signals of the other operators are connected, with this differen cc that the wire 16,which is the individual wire for the chief operator, may be common to all of the switching mechanisms at any one answering-board, thus giving the chief operator a single an uuuciator for each board-section or any desired number.

The basic idea underlying the present invention and forming the subject of the previous application above referred to is that of connecting a cord-circuit to a calling-subscribers line, said cord-circuit containing selective mechanism which thereupon passes under the control of the subscriber and by means of his signal mechanism is operated to prolong his line to a terminal device at the wanted board without any further act on the part of the operators. In this case I is an answering-plug forming the terminal of a cordcircuit 10 11, B is the selective mechanism connected with this cord-circuit, and P P are calling or connecting plugs adapted to be connected by said selective mechanism to the plug P each when the board at which it is located contains the terminal of the wanted line. through the mechanism of the selector to an arm f carried on the spindle of a toothed wheel f adapted to be rotated in one direction by a pawl b on the end of a spindle 71", attached to an armature I), normally retracted from the magnet b by a spring b the wheel f being adapted to be rotated in a reverse direction in order to bring it around again to the point shown, with arm f resting against a suitable stop, by a springf.

F is a ring frame of insulating material having saw cuts in its face arranged so as to be tangential to the outer circle swept by the arm f This ring frame serves as a point of attachment for the fixed end of the retractingspring f and also for a stop-pawl D, of which more will be said hereinafter. In each saw cut is secured a contact-spring having a curved end adapted to form a good contact with the end of the arm f.

The conductor 10 of the cord-circuit passes directly from the sleeve of the plug P to all of the other board-sections, passing at each through the spring-contact of a ringing-key K and having at each a branch leading to the individual plug thereat, the branches being lettered 10 10", &c. This conductor 10 constitutes a common return for the cord-circuit, being adapted to be paired with any of the other cord conductors, of which one is provided for each board-section. These individual conductors 14 15 16, &c., are connected to the springs f, the conductor 16, extending to the chief operator-s board, being always connected to the first spring.

Connected across the wires 10 11 at the answering-board is a conducting-bridge 12, containing the windings of a coil of high impedance E, from the middle point of which a wire 13 is led to the magnet Z) and thence by wire 20 to the ground-wire 4, through the generator G, and to ground. From the wire 13 a short wire 19 is led to one of two back contacts of the armature Z), the other of which is connected through wire 18 with a contact (1 within the range of movement of the lever D, which carries the selector stop-pawl. A twin cont-act d, also within said range of movement, is connected by wire 17 through lamp L to ground.

At each switchboard-section to which the circuits from plug Pextend a signal-controlling relay C O, &c., is provided, having its windings included in a circuit 23, extending from the bus-bar 5 to the middle point of the winding of a suitable impedance-coil E E &c. Each of these impedance-coils has one The cord conductor 11 is connected,

III)

extremity of its winding permanently connected to the individual wire leading to its board from the selector, while the other extremity is connected to a normally-open contact in'a switch adjacent to and intended to be operated by the corresponding callingplug. Thus coil E is connected between conductor 14 and contact 71 in the switch H. This switch proper consists of two springarms 7L and h, connected together mechanically, but insulated electrically, The spring h is permanently connected tothe conductor 10, while spring h is permanently connected to a lamp L and by wire 27 to ground. The latter spring normally rests, when the plug P is in its seat, against a contacth, connected through wire to the front contact 0 of the relay 0. The spring is adapted when the plug is removed from its seat to leave the contact h and rest upon'contact h connected by wire 26 to the back-stop c of armature c of the relay 0; This armature is connected by wire 24 to wire 23 and so to bus-bar 5. The spring h, constituting a normally-open terminal for the wire 10% is adapted when the plug is removed from its seat. to rest against contact 71?, thereby connecting the open end of the winding E to said wire 10.

The ringing-key K, besides the contacts included in the circuit of wire 10, has a second pair included in the individual wire 14, and when its springs 10 are spread both said conductors 10 and 14 are broken and the plug P is connected directly through wires 21 22 to the alternating-current generator G.

As a convenient means for listening in I have shown the operators telephones O and O as connected to pairs of contacts underlying pivoted switch-arms D and D extending into the seats of plugs P and P respectively. Twin contacts are connected, respectively, to conductors 10 and 14. The normal position of the levers D D is as shown; but if either plug be depressed in its seat before being removed therefrom its lever-switch will be depressed to connect the operators set across its cord conductors.

The operation of the system thus described is as follows: Suppose subscriber Y desires to converse with subscriber X. He looks in his directory and finds that Xs number is 2-56, which means that Xs jack is No. 56 on the second section. Y sets his transmitter W so as to send three impulses. This is not necessarily known to him, as his actual manipulation consists merely in moving around a pointer until it stands at the figure 2. It will be observed that the pens of the signaling mechanisms normally rest upon teeth, and the parts are so arranged that whenever a mechanism is set its pen will rest upon a tooth. It is the number of breaks andnot the number of makes which determines the movement of the selector. Having set the instrument, Y removes his receiver from the hook S, whereupon a circuit is immediately closed and current flows from the generator G by wires 5 and 4 to annunciator A, by wire 3 to line-wires 1 2, in parallel through the switch-arms S and S and the local talkingcircuit, through the wire 7, the signal-wheel, wire 8, magnet w, wire 9, and ground back to l the generator by wire 6.- The magnet A, having, as before described, a greater number of turns than the magnet w, attracts its armature and displays its signal. The magnet w, however, having few turns, is powerless to attract its armature with the small current which the resistance in the circuit permits to flow. The operator at the right-hand switchboard, perceiving the signal, inserts the plug P in the jack J and turns to other business.

The entrance of the plug spreads the springs j away from the anvil j and forms a new circuit as follows: from generator G, by wires 5 and 4, to wire 20, wire 13, magnet b, winding of coil E in both directions, bridge-wires 12, conductors 10 and 11, line-wires 1 2, switchlevers and local circuits, wire 7, signal-wheel, wire 8, magnet w, wire 9, and by ground and wire 6 back to the generator. The magnet b and the magnet to are approximately of the same resistance, both being low-wound. Consequently there is a sufficient flow of current to energize both magnets. The armature b is attracted and moves the tooth b to the right far enough to engage the next succeeding tooth of the wheel f, while the armature w is removed from engagement with the signal mechanism and the wheel starts to return to normal under the influence of its drivingspring. At the first break the armature b is retracted by its spring, drawing the spindle b and the pawl 19 with it and turning the wheel f the space of one tooth, which is suf- -ficient to bring the arm f into contact with the first one of the springs f, connected to wire 16. At the second break the wheel and arm are moved another step and at the third break still another step, the arm then resting upon the third spring, which is connected with the wire 15, leading to plug P The wheel of the mechanism W having then reached zero, the circuit remains closed and the armature I) remains attracted, the magnet 71 thenceforth serving as a clearing-out relay. With the apparatus in this position a new circuit has been formed from generator G to lamp L as follows: from the generator by wire 5 to conductor 23 and relay-magnet O, thence through one-half of the winding of coil E to conductor 15, and through the selector mechanism by way of the spring and the arm f to conductor 11, line-wire 2, and so to subscribers station and ground back to generator. The relay 0 attracts its armature, closing the following circuit: from the generator G, by bus-bar 5, to conductor 23, to branch 24, through the armature 0, contact 0, wire 25, contact h, spring h to lamp L wire 27, and ground back to the generator. It will be understood that no such action as this took place at the other sections as the arm f passed over successive springs, because the movement of the signaling mechanism \V is sufficiently rapid not to leave the arm for more than afraction of a second on any one spring. The lamp L becoming incandescentapprises the operator that a connection has been initiated on the plug line 0 The operator thereupon depresses the plug in its seat, thus bringing the lever D onto its contacts and bridging her telephone set across the circuit. Inquiring the number wanted, the subscriber, who has been waiting with his receiver at his ear, responds 56. The operator then removes the plug P, on which, it will be observed, she already has her hand, and places it in the jack of Xs line. Having done this, she depresses the key K, and thereby throws calling-current upon theline to ring js bell. A button may be provided and preferably is provided in connection with the lever D for the purpose of enabling the operator to listen in from time to time; but as that forms no partof the present invention it is not shown. By the removal of the plug P from its seat the switch His allowed to shift over, connecting the normally-open end of the coil E to the conductor 10",and the lam p-wire 27 to the wire 26 through contact 7L3. Both magnets C and I) hold up their armatures during the continuance of the conversation, and as the coils E and E constitute bridges of the through metallic circuit neither subscriber by hanging up his receiver can operate these magnets to give a clearing-out signal. Both receivers must be hung up and both grounds removed from the united circuit before the magnets will release their armatures, for obviously if there is a ground at either end of the circuit it is sufficient to permit generator-current to continue flowing. WVhen, however, both subscribers have hung up their receivers, and thus cutoff their grounds, both magnets b and C will release their armatures and the following circuits ,will be closed: from generator G, by bus-bar 5, to wire 4, branch 20, branch 19, armature 1), wire 18,,contact d, lever D, contact d, lamp L, and wire 17 to ground and back to generator; also, from generator, by bus-bar 5, to wire 23, branch 24, armature 0, wire 26, contact h", spring 7L, wire 27, lamp L and ground back to generator. Both lamps L and L will thus be lighted, and each will continue lighted until its corresponding plug has been removed from the line-jack. \Vhen the plugPis replaced in its seat, it depresses the lever D and breaks the circuit of the lamp L, also removing the stop-pawl from the wheel f and permitting the wheel to return to zero. It should here be stated that when in its retracted position the pawl 19 is disengaged from the teeth of the wheel. \Vhen the plug P is returned to its seat, it again displaces the switch H and breaks the lamp-circuit 27 between spring 71, and 7L3, returning the spring to the cont-act h for further calls.

IIaving described my invention, what I claim, and desire to secure by Letters Patent of the United States, is

1. In a telephone-exchange system, a subscribers station, a central station and a metallic circuit interconnecting the two, a telephone set at the subscribers station connected in the metallic circuit, asignal-transmitting apparatus at the subscribers station adapted to be connected to both limbs of the metallic circuit to determine a flow of signalingcurrent therethrough in parallel, a telephone-circuitatthe central station adapted to be connected to the subscribers metallic circuit to form an extension thereof, a plurality of signals associated with said circuit, and a selective signal mechanism also associated therewith, controlling said signals, and adapted to be brought into connection with both sides of the subscribers metallic circuit to respond to the signalingcurrent therein, substantially as described.

2. In a telephone-exchange system, a plurality of switchboards and subscribers metallic circuits connected thereto, a telephone set at each subscribers station included in the metallic circuit, a source of current, and a signaling device at each subscribcfls station adapted to be connected to both limbs of the metallic circuit to control the flow of current therethrough in parallel, connective telephone-circuits for the switchboards each having one terminal at one board, and a plurality of branch terminals at other boards, a signal associated with each branch terminal, and a selective mechanism adapted to control said signals and connected to both sides of the connective circuit, the whole being so arranged that when a connective circuit is connected to a subscribers line in answer to a call the selecting mechanism is placed under the control of the subscribers signal mechanism, substantially as described.

3. In a telephone-exchange system, a central station having a plurality of switchboards and subscribers metallic circuits terminating in spring-jacks thereon, a telephone at each subscribers station in the metallic circuit, together with means to determine a flow of signaling-current through the telephone neutrally and through the limbs of the metallic circuit in parallel, a connective circuit at the central station having an answering-plug at one board and connecting-plugs at other boards, a selective mechanism having a connection to said answering-plug, and branch connections to all of the connectingplugs, a signal for each connecting-plug controlled by a magnet connected to its branch and a magnet controlling the selective mechanism and so connected to the answeringplug that when said plug is inserted in a linejack the magnet is thereby brought into connection with both limbs of the subscribers metallic circuit to respond to the signal-current therein, substantially as described.

4. In a telephone-exchange system, a plurality of switchboards and subscribers circuits terminating in sprung-jacks thereon, connective circuits for such sw'itchboards each having an answering-plugfat one. board and connecting-plugs at theother boards, a

selective switch connected with the answeringplug and adapted when actuatedto complete the circuit to any desired-one. of? the connecting-plugs, ajm'agnet'permanentlyconnected to the answering-plug circuit and controlling said selective switch, a supervisory;

signal also underfthe control of'saidmagnet, and means at each subscribers station for de-.

termining the flow of signaling-current over the line both before and aft'er a conversation, substantially asdescribed.

current in the line-circuit; a connective circuit at the central station adapted to be connected to the subscribers line inresponse to his call, a supervisory signal associated with the connective circuit, a relay as (Land a switch as H, the relay being electrically con,- nected tothe saidiconnecti've circuit and adapted to be placed under control of the sub scriber when connection is madewith his line a calling-plugal'so connected to the connectmally open at the switch and normally closed at the relay, and the othernormally closed at the switch and open at the relay, whereby when the relay-is first energized the signal is displayed, when connection is completedthrough the calling-plug to the line desired; the signal is retired, and when the relay is. finally deenergized by the cessation of current in the subscribers line the signal is again this. 20th day'of- April, 1899.

displayed, substantially as described.

6. In a telephone-exchange system, a plurality of switchboards and subscribers metallic circuits terminating in spring-jacks thereon, means at each subscribers station to determine a flow of signaling-current over the line-wires in parallel, a circuit extending between the various switchboards, having an answeringplug at one board and connectingplugs at other boards, a selective multipleterr'n inal switch, two conductors extending from said answering-plug,one to all the boards as a common return for all the connect-ingplugs, andthe other to the multiple-terminal switch from each of whose terminals an individual wire extends to one of the connecting plugs, a signal-relay for each connecting-plug I normally connected to its branch wire, and

means actuatedin; the use of saidconnectingplug to connect the relay to the common returnof the answering-plug, whereby the relay may be controlled from theselectiveswitch through the branch Wire to give an advance signal, and is thereafter left in position-to serve as the subscribers clearing-out signal, substantially as described. r I v r 7. In a'telephone-e'xchange system, subscribers stations and a central station, and

metallic line-circuits interconnecting them;

mine a flow of signaling-current between the be connected with the two line-wires so as to control talking-currents therethrough in series; switching mechanism at the central oifice adapted to prolong the metallic circuitof any subscriber to form a connection for talking purposes with another subscribers line; and magnetic means for controlling said switching mechanism and operating the same,adapted to be controlled from the snbscribers'line', beingv'connected thereto neutrally, so as to be unaffected by, and in its turnnot t0 afiect the talking-current in the metallic circuit, but to beaffected by the signaling-current passing over the line-wires in parallel, as described. In testimony whereof I have hereunto set my'hand, in the presence of two witnesses,

EDWARD E 'OLEMENT. Witnesses: v I SPENCER B. PRENTISS, W. BERTRAND AOKER.

. means at each subscribers station; to deter-.

75 station and the central office over his two linewires inparallel as a single conductor, a telephone at each subscribers station adapted to. 

